Apparatus for testing saw blades



Jan. 17, 1928. 1,656,452

. y A. swxNG APPARATUS FOR TESTING SAW BLADES Filed Jamas, 1924 2 sheets-sheet 1 /l//f//f/f//z/ Jan. 17, 192s'.

A. swlNc:` APPARATUS FOR TESTING SAW BLADES Fuga JmLzs. 1924 2 sheets-sheet 2 l /l/I/ l l lNvEN ToR LTI/9 Patented Jan. 17, 1928.

i UNITED STATES PATENT OFFICE.

ALFRED SWING, F EAST ORANGE, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS,

T0 FEDERATED ENGINEERS DEVELOPMENT CORPORATION, A CORPORATION 01"" DELAWARE.

APPARATUS 'FOR TESTING SAW BLADES.

application mea January ze, 1924. serial no. 688,765.

This invention relates to improvements in apparatus for testing saw blades, particularly to apparatus for magnetically detecting defects in the blades before the blades are finished. In the manufacture of saws,

there is considerable time and labor expended in producing the finished blade from a stamping, only to discover that the finished-l blade is faulty, usually caused by a crack in the toothed edge of the blade. Most of these flaws are too slight to be visibly detected prior to the time that the blade has been finished, and polished, and it is an object of the present invention to` provide means for magnetically detecting flaws in the blades as soon as the blades are blanked out, and thus permit defective blades to be discarded before the finishing operations have been performed.

It is a further object of the invention to provide means for testing the blades which will in no way injure or strain good blades.

It is a further object of the invention to provide testing means which may be used by an unskilled operative. It is a further object to provide testing means which will be unlikely to get out of order, which will be simple and practical in construction, durable and efficient in use, and comparatively inexpensive to manufacture.

With these and other objects in view, the invention consists in certain novel features of construction and combinations and arrangements of parts as will be more fully hereinafter described and pointed out in the claims.

In the accompanying drawings,

Fig. 1 is a top p an view of my lmproved apparatus for testing saw blades,

' .Fig. 2 is an enlarged detail plan view of part of the apparatus, parts being broken awa and in section for clearness,

Fig. 3 .is a transverse sectional view on the line 3-3 of Fig. 2,

Figs. 4 and 5 are detail sectional views on the line 4, 5 4, 5 of Fig. 3, showing the detecting means in inoperative andoperative positions,

Fig. 6 is a fragmentary plan view of the detecting means and showing a defective saw blade in position, and

Fig. 7 is a wiring diagram.

Referring with particularity to the drawings, I have used the reference numeral 10 to designate the base of my improved apparatus. An inclined brace 11 is secured at its forward edge to the forward edge of the I l base, extending longitudinally thereof, and .supportlng the forward upper edge of an inclined platform 12 Whereon the saws 13 to be tested are laid. Rising from the rear of the intermediate portion of the base 10 1s a housing 14 for the detecting mechanism and the platform 12 is cut away to accommodate Vthe housing. The lower rear edge of the platform rests upon the base and at opposite sides of its cut-away portion, the platform is provided with longitudinally extending vshoulders 415 against which the toothed edge of a saw is adapted to abut t0 retain the saw in proper position for testmg.

The housing 14 is formed with a front opening 16 and at that portion ofthe platform 12 facing the opening, the platform is inlaid with a sheet 17 of insulating material. Platform 12 and sheet 17 are cut away as at 18 to accommodate the forward end of a balanced lever 19 carried by a rock shaft 20, which is delicately mounted in bearings 21 in brackets 22. At its forward end, the lever 19 carries a soft iron armature 23 and at its rear end carries a contact member 24 adapted to make contact with a stationary contact member 25 secured upon a post 26 within the housing 14. Movement of the lever 19 in the opposite direction is limited by the engagement of the lever with va stop 19.

I provide means yfor causing a magnetic flux to pass through that portion of the saw blade which is disposed immediately above the cut-away portion 18 of the platform.

One convenient means of accomplishing this purpose comprises an electromagnet consisting ofa-U-shaped core 3() having its ole pieces secured in the platform and exten inc' through the sheet of insulating 'material l? into contact with a saw blade -on the platform. Energizingr coils 31 on the arms of the core will create a magnetic ux through the core and through that portion of the edge of the saw blade between the poles of the-core. if

If the toothed edge of the saw blade is homogeneous throughout as in Fig. 4, there will be no'leakage of magnetic flux from 'that portion of the blade adjacent the armaleast resistance will result in attracting the armature 23 to the saw blade, as seen in Fig. 5, and through the intermediacy of the armature unsuspected flaws in the blade may be readily determined. It will be apparent to an 'one familiar with magnetic testing that tliis movement of the armature may be used to indicate visibly or audibly in any suitable manner that there is a defect in the blade.

.For purposes of illustration, I have shown a relay Ll() secured within the housing 14 and adapted to operate a signal lamp 41 on the front of the housing. The means b which the armature controls the signal iamp is shown most clearlyin the wiring diagram of F ig. 7. In this ligure, it will be seen that the armature 23 when it is attractedagainst the blade closes a relay circuit r through a battery 'B and that closing of this relay circuit will in turn attract an armature a to li ht the signal lam 41. The same battery which is used to ener'ize the relay circuitl ma also be used in energizing the field pro ucing coils 31, a suitable switch a in the battery line being closed prior to the testing operation.

For convenience in obtaining access to the energizing coils, a removable plate 50 ma be secured over an opening in the longitudinally extending forward brace 11. The platform 12, base 10, brace 11 and housing 14 are preferably formed of non-conducting material and the use of the insulati sheet 17 serves -to concentratethe magnetic fiuxc passing between the poles of the armature 30 at the toothed edge of the saw blade. The

blade may be tested by sliding the same along the platform so that every portion of the toothed edge is moved over the armature 23. Whenever a crack or flaw occurs in the edge of the blade, signal lamp 41 will light.

I am well aware of the fact that compass needles and other magnetized detectors have been previously used for detecting inhomogeneities in magnetizable objects, and Wish to call attention to the fact that the detector 23 is of magnet-izable materia-l as opposed to magnetized material. The use of the soft iron armature of low reluctance permits the armature to be placed directly in the ma netic field without being affected by the or nary leakage from a closed ma etic circuit and at the saine time, it will e extremely sensitive to magnetic leakage caused by flaws. In speaking of a magnetizable detector in 1j ects,

lpositioned in operative l tested thereby is immaterial to the invention.

Furthermore,

the apparatus herein shown is subject to an iniinite variety of structural modifications without departing from the invention, and hence I do not wish to limit myself to the precise details set forth, but shall consider m self at liberty to make such changes an alterations as fairly fall within the spirit and scope of the appended claims.

I claim:

1. Apparatus for testing magnetizable objects, comprising 'an inclined platform for supporting the object to be tested, said lat form having a cut-away portion over w ich that portion of the object to be tested ex'- tends, means for magnetizing the object, detecting means movable in the cut-away portion of the platform and sensitive only to magnetic lea age caused' by inhomogeneities in the object.

2. Apparatus for testing magnetizable objects, comprisin an inclined platformv for supporting the o ject to be tested, said latform having a cut-away portion over w 'ch that portion of the object t be tested extends, means for magnetizing the object, detecting means movable in the cut-away portion of the latform and sensitive only to magnetic lezili'age caused by inhomcgenei- 105 ties in the object, and indicating means controlled by movement of the detectin means.

3. Apparatus for testing magnetized obincluding detecting means comprising in armature of low magnetic reluctance 110 roxmity to a magnetized object, a pivotedp lever on which said armature is borne,`contact making apparatus carried by said lever, and signal means controlled by said contact making apparatus.

4. Apparatus for testing a magnetizable object including means for subjecting the object to the action of magnetic field, a movable magnetizable detector adjacent the ob- 'ect adjusted to be movedonly by magnetic 120 leaka e due to distortion of the field about said o ject.

5. Apparatus for testingv a magnetizable object comprising meansv for producing a magnetic field about the object, a movable 125 magnetizable detector in the field sensitive only to magnetic leakage from said. object, an means for indicating movement of the detector caused by said magnetic leakage.

6. Apparatus for testing a magnetizable 130 object comprising means for producing a magnetic field about the object, a magnetizable detector of low magnetic reluctance ,mounted to move toward and from said object, and means for indicating movement of the detector caused by distortions in the field.

7. Apparatus for testing a magnetizable object comprising means for producing a magnetic field about the object, a soft iron detector in the field, a mounting for the detector permitting movement of the detector toward and from said object, and means for indicating such movement of the detector caused by distortions in the eld.

8. Apparatus for testing a magnetizable object comprising magnetizing means having exposed iux conducting portions positioned for engagement with said object, and iux leakage detecting means including a movable member having a fiux sensitive portion positioned in such proximity to the path of said object that flux leakage from said object will be efective to move said movable member.

ALFRED SWING. 

